The recent trend towards miniaturization of circuitry has resulted in an increase in the density of wiring both inside and outside electronic instruments and a miniaturization of terminal sections.
This movement towards the miniaturization of instruments for the transmission of high frequency or rapidly rising pulse signals creates a requirement for impedance matching to prevent the reflection of such signals in the line itself or at the terminal or connector sections.
Space in miniaturized instruments is so limited, for example, that a flat cable must accomodate about 60 conductors in a width of 30 mm. It is very difficult, time-consuming and requires painstaking effort to effect impedance matching, pull-up, pull-down, etc., at terminal sections or near connectors on such cables by soldering such elements as resistors and condensers to each conductors.
In view of the above situation, the present inventor has carried out investigations on high-density wiring inside and outside miniaturized electronic instruments, and especially on materials suitable for wiring of, and connection to, sections requiring impedance matching, pull-up, pull-down, etc. This has led to the discovery of flat cables which are free of the various defects mentioned above which are found with conventional wiring materials, and which may be used in a variety of forms .